Blood tests are ordered for many reasons: to diagnose disease, screen for illness, monitor the effectiveness of a therapy or the side effects of a therapy. If you are healthy and having blood work done, "you want to know that whatever they're looking for screening-wise is really going to help you live longer and healthier," says Dr. John Epling, associate professor and chair of Upstate's Department of Family Medicine.

Epling spoke about blood tests at the Health Link seminar series, simplifying some of the mysteries.

For instance... wonder why multiple tubes of blood may be collected? Because to keep blood from clotting, so that it can be analyzed at the lab, chemicals have to be added to the samples. Adding chemicals alters the makeup of the blood, so separate samples are collected for specific tests.

A "CBC" is a "complete blood count," which identifies the number and type of cells in the blood. It can reveal anemia, infection and bleeding disorders. If you are identified as anemic, Epling says the source of the anemia must be investigated. "It's not enough to just take iron supplements," he says. Anemia could be caused by a loss of blood, a nutritional problem or cancer. To find out if it is caused by a lack of iron, a separate blood test can gather a ferritin level.

Check Health Link to learn about upcoming talks.